New York ? Two years ago, the people at TLC wouldn’t have traded spaces with anybody.

The home makeover show “Trading Spaces” was one of those cultural phenomena most tiny cable networks can only dream about, and TLC rode the wave to record ratings and attention.

Then it crashed.

Doomed by overexposure, imitation and changing tastes, “Trading Spaces” lost much of its audience, and TLC has paid the price. Its president, Roger Marmet, was ousted. Some two dozen jobs were lost throughout Discovery Communications, TLC’s parent company. And TLC is struggling to change the perception that it’s a network in free fall.

As they pick up the pieces, the executives at Discovery Communications are left to ponder whether this was avoidable, or simply the inevitable effect of gravity, TV style.

“You can’t get to the stratosphere and stay there,” said John Harvey, senior producer at “Trading Spaces.” “It rarely happens in this industry.”

The show’s Saturday night viewership has nose-dived from 659,000 last year to 429,000 this year, according to Nielsen Media Research. The decline is 46 percent among the youthful demographic that advertisers seek. This past weekend the show debuted in a new format, without perky host Paige Davis.

Meanwhile, ABC’s “Extreme Makeover: Home Edition” — starring former “Trading Spaces” carpenter-hunk Ty Pennington — is a hit that drew 15.5 million viewers last week.

At its peak, TLC was running “Trading Spaces” episodes as many as 10 times a week. Harvey’s production company was churning out themed specials to feed an insatiable hunger. Davis’ face was on magazine covers and in TV commercials.

Both TLC and competitors sought to duplicate the success. At one point, Discovery President Billy Campbell counted some 28 replicas of the show all over the dial. Even VH1 tried making over rock stars’ homes.

“Did we overexpose the show and the genre?” Harvey asked. “I think the answer is yeah. Here’s the dilemma that every network doing this faces: You can stand back and be pristine and say we’re going to jealously guard this … But if you do that, everyone will still cherry-pick and steal your ideas. That’s what happens when something is a success.”

The classic case of overexposure is “Who Wants to Be a Millionaire,” which put ABC in such a deep hole it is only recovering this season.

Campbell argues that TLC didn’t overexpose “Trading Spaces.” The cumulative effect of all those imitators hurt the most, he said.

“It’s always tempting when you have success,” he said. “Look how many people tried to copy ‘Friends.’ Look how many people tried to copy ‘Seinfeld.’ I saw ‘Grey’s Anatomy’ the other night, and it’s basically a young person’s ‘ER.’ As a programmer, it’s hard not to emulate success because that’s your goal, to make successful programming.”

“Trading Spaces” remains on the air, and is comfortably successful by cable standards. It’s just not a phenomenon.